Ignition device for high pressure discharge lamps

ABSTRACT

This is an ignition device for a high pressure Mercury or Sodium Discharge Lamp. The device consists of a thermal switch which applies the starting voltage to the lamp after the switch heats up. The thermal switch is located outside the lamp.

United States Patent 1 [111 3,740,686-

Jarrige, deceased et al. June 19, 1973 i IGNITION DEVICE FOR HIGH PRESSURE [56] References Cited DISCHARGE LAMPS UNITED STATES PATENTS [75] Inventors: Georges Roger Jarrige, deceased, 3,496,508 2/1970 Meijer 337/22 late of Bagneux, France by Jeannine 2,022,406 11/ 1935 Cook Germaine Jarrige, adminigtratrig 3,546,536 12/1970 Umin t. Dat Nhiep Nguyen, 2,274,399 211942 Cook chatenayMaiabry France 2,228,210 1 1941 Hays 337 22 73 Assignee: ITT Industries, Inc., New York, Primary E A. Gilheany Assistant Examiner-F. E. Bell 22 Filed; June 7 1971 Attorney-C. Cornell Remsen, Jr., Walter J. Baum, I

[ pp o PaulW.Hemmingcretal.

[30] p 57 ABSTRACT Foreign Apphpatlon Pmmty Data This is an ignition device for a high pressure Mercury or Sodium Discharge Lamp. The device consists'of a l F an "7023616 thermal switch which applies the starting voltage to the lam after the switch heats u The thermal switch is 52 .u.s. 337/22, 317/51 waged outside the lamp p v t [51] Int. Cl. .L H0lh6l/00 i [58] Field of Search 337/22, 23, 103; 1 C a m, 2 a ing F gures ENS/74,75, i25,24 ();314/ll;3l7/50,5I,92,

BACKGROUND OF THE INVENTION The present invention concerns an igniting device for electrical discharge lamps containing mercury or sodium vapor at high pressure.

It is known that the electrical discharge between the two electrodes of a lamp with mercury or sodium vapor at high pressure is set up only if a voltage equal to or higher than the arc striking voltage is applied during a short instant to the said electrodes, the striking voltage being higher than the potential difference which exists once the arc'is established and also higher than the power supply voltage to which the lamp is connected. Thus, numerous devices enabling the ignition of such lamps have been described, said devices being based upon the use of different principles such as the building up of an electrical pulse of sufficient amplitude for striking the discharge, the preheating of the electrodes which decreases the striking voltage, the preionization by adding a third electrode close to one of the two first electrodes. This last solution is generally adopted for high pressure mercury vapor lamps which do not comprise additions of metallic halogenides.

In the case of high pressure sodium vap'or lamps, it is known to incorporate into the lamp a thermal switch which short-circuits the lamp when it is off, and which opens only a certain time after the voltage has been applied to the ballast; the opening of this switch connected to the self-induction circuit of the ballast creates an electrical pulse of high amplitude which is applied to the lamp. Such 'a device presents the drawback that owing to its incorporation into the lamp, its failure alone leads to the change of the lamp; besides, the great quantity of heat dissipated during operation and the thermal inertia, of the whole assembly maintain the switch open a long time after the lamp is off, this making impossible the re-striking for a longer than desirable period of time. I

, Igniting devices with electronic components which supply an electrical pulse-of sufficient amplitude have also been described, these devices presenting the draw back of continuing to operate when the lamp has just failed; this may create breakdowns in the electrical circuits as well as the transmission of parasites.

SUMMARY OF THE INVENTION One object of the present invention is an igniting device for high pressure sodium or mercury vapor lamps enabling a quick restriking under hot condition.

Another object of the present invention is an igniting device which protects the electrical circuits against any break-down even .in case of failure of the lamp.

According to the invention there is provided an igniting device for a high pressure vapor lamp having first and second terminals comprising, a self-induction type ballast having first and second output terminals, a thermal switch having first and second arms coupled to said first and second ballast terminals and to said first and second lamp terminals respectively, said first arm being stationary and said second arm having one fixed end and one movable end, said movable end being in contact with said first arm when said switch is closed and out of contact with said first arm when said switch is opened, and over-voltage protecting means connected in parallel with said lamp and to said movable end, said .2 I protecting means having a higher breakdown voltage than the igniting voltage of said lamp.

The above-mentioned and other features and objects of this invention will become more apparent by.reference to the following description taken in conjunction with the accompanying drawings, in which: i

. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents the electrical diagram of theigniting device according to the present invention; and

FIG. 2 represents a particular embodiment thermal switch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The igniting device of the high pressure mercury or sodium vapor lamp 2 comprises, beside the ballast 1 of the self-induction-type usually used for stabilizing the lamp at its operation point, a thermal switch 3 and a lightning protector device 4.

The ballast 1 comprises two input terminals A and B connected to the supply line through a switch I and two output terminals A and B; the ballast comprises an induction coil 5 of suitable value for obtaining a stable operation point of the lamp 2. Q

The arm6 of the thermal switch 3 is fixed andconnected to oneof the output terminals of the ballast 1, for instance the terminal A, as well as to one of the two electrodes of the lightning protector device 4 and of the lamp 2; the arm 7 of the switch 3 is a moving part and constitutes the arm or finger distorted under the action of heating due to the electrical current which flows i 9 of the moving arm 7 is connected to the secondterminal B of the ballast. Y

' The lightning protector device 4 is of any known type I and its features are such that its striking voltage is switch 3 is closed. As soon as the switch I is closed, a

current flows through the coil 5 and the movingarm 7 of thermal switch 3; this heats and, after a certain time interval, the moving end 8 of arm 7 moves away from the fixed arm 6; due to the energy stored in the coil 5 of the ballast, an over-voltage'appears at the terminals of the contacts of the switch 3 when it opens; this overvoltage is applied to the lightning protector device 4 and to the lamp 2 which ignites. The lamp 2 remainson since its two electrodes are connected one directly to the terminal A and the other to the terminal B through end 8 of moving arm 7. The lamp current flows through this moving arm 7 which remains thus in its open position i.e., the switch 3 remains open.

If the lamp 2 is off by opening the switch I, no current flows through the moving arm 7 which returns to the rest, or closed, position after a rather short lapse of time, thus closing the switch and enabling a re-striking.

of the If the lamp 2 is removed due to a failure, the switch 3 returns to the, or closed, rest position and initiates a re-striking since the switch I has remained closed; however, the over-voltage which appears between the contacts of the switch 3 is absorbed by the lightning protector device 4 and protects the leads and 11 against any breakdown.

FIG. 2 gives a particular embodiment of the thermal switch. The identical elements of the FIGS. 1 and 2 bear the same references. In this FIG. 2, the thermal switch constituted by the arm 6 and the moving arm 7 is arranged inside an enclosure 15 such as a glass bulb in which a vacuum has been formed (pressure close to 10' torr, for'instance). The switch is carried by the rigid conductorsl7 and 18 which are fixed in the lower part 16 of the bulb and which are connected respectively, inside the bulb, to the fixed end 9 of the bimetallic strips, and to'the fixed arm 6; outside the bulb, the conductors 17 and 18 are connected respectively to the terminals B and A of the ballast. A third conductor 19 crosses through the lower part of the bulb and is connected, by means of a flexible wire 20 to the moving end 3 of the bimetallic strip 7; the other end of the conductor 19 is connected, outside the bulb, to one of the the two electrodes of the lightning protector device and of the lamp. The element 21 contained in the bulb is the getter carrier which has been used for improving the vacuum. I

The igniting device described hereabove is intended .particularly for high pressure sodium vapor lamps; however, itmay be used for high pressure mercury vapor lamps with. or without addition of metallic halogenides. ln the high pressure mercury vapor lamps without addition of metallic halogenides, ignition is generally obtained by means of a third electrode which would not be required if the device according to the invention was used;

While the principles of' the above invention have been described in connection with specific embodiments and particular modifications thereof, it is to be clearly understood that this is made by way of example and not as a limitation of the scope of this invention.

What is claimed is:

1. An igniting device for a lighting circuit including a high pressure vapor lamp having first and second terminals comprising:

a self-induction type ballast having first and second output terminals;

a thermal switch enclosed in a hermetically sealed vacuum enclosure separate from said lamp and said ballast so that said lamp is extractable from said circuit when malfunctioning without removing said switch from said circuit, said thermal switch having first and second arms coupled to said first and second ballast terminals and to said first and second lamp terminals respectively, 1 said first arm being stationary and said second arm having one fixed end and one movable end, said movable end being in contact with said'first arm when said switch is closed and out of contact with said first arm when said switch is opened, said switch providing a short circuit across said lamp when closed to generate heat within said enclosure; said second arm being a bimetallic strip movable to open said switch upon heat being stored in said hermetically sealed enclosure upon current flowing through said switch .whensaid switch is closed; and over-voltage protecting means connected in parallel with said lamp and to said movable end, v said protecting means having a higher breakdown voltage than the igniting voltage of said lamp. 

1. An igniting device for a lighting circuit including a high pressure vapor lamp having first and second terminals comprising: a self-induction type ballast having first and second output terminals; a thermal switch enclosed in a hermetically sealed vacuum enclosure separate from said lamp and said ballast so that said lamp is extractable from said circuit when malfunctioning without removing said switch from said circuit, said thermal switch having first and second arms coupled to said first and second ballast terminals and to said first and second lamp terminals respectively, said first arm being stationary and said second arm having one fixed end and one movable end, said movable end being in contact with said first arm when said switch is closed and out of contact with said first arm when said switch is opened, said switch providing a short circuit across said lamp when closed to generate heat within said enclosure; said second arm being a bimetallic strip movable to open said switch upon heat being stored in said hermetically sealed enclosure upon current flowing through said switch when said switch is closed; and over-voltage protecting means connected in parallel with said lamp and to said movable end, said protecting means having a higher breakdown voltage than the igniting voltage of said lamp. 